The present invention relates generally to the art of grinding, and more particularly to the art of adjusting a grinding wheel to compensate for wear.
U.S. Pat. No. 2,490,848 to Vassler discloses an apparatus for simultaneously grinding a plurality of like knife frame elements. The apparatus comprises a reciprocating work table and an elongated tubular grinding wheel, cam-mounted to grind curved surfaces.
U.S. Pat. No. 3,512,306 to Phillips discloses a glass threading apparatus with a continuously rotating grinding wheel. A workpiece supported at the end of a shaft can be rotated and advanced relative to the grinding wheel. The shaft is mounted in a support mechanism which is pivotally supported about two mutually perpendicular axes so that the orientation of the shaft can be adjusted relative to the grinding wheel.
U.S. Pat. No. 4,376,356 to Everett discloses abrasive disc saws improved by means for adjusting the amount that the saw moves toward and away from the work so that the saw does not "cut air".
Large glass sheets are often coated with a metal-containing film. Various metal and metal oxide films are useful for controlling solar energy reflectance and transmittance. When such coated glass sheets are fabricated into window units, it may be desirable to remove a portion of the film along the perimeter of the coated glass surface where sealants or adhesives are applied in order to provide direct contact with the glass to prevent reaction with the film.
A preferred method for removing such a strip of film is by grinding. In general, a grinding wheel is guided along the edge of the coated surface to remove the film by abrasion. The abrasive properties of the grinding wheel are determined by the particular film to be removed. Typically, the grinding wheel should be sufficiently abrasive to remove the film without significantly affecting the underlying glass surface. The pressure on the grinding wheel is preferably kept at the minimum required to remove the film in order to minimize the rate of wear of the grinding wheel. Nevertheless, the grinding wheel surface does gradually wear away.
If the axis of a grinding wheel and coated glass are in fixed position relative to each other, eventually the grinding wheel will wear away to the extent that there will be insufficient contact with the coated glass surface to remove the film. It is well-known in the art to compensate for grinding wheel wear by raising the substrate. In the alternative, the grinding wheel and substrate are not in fixed position relative to each other. For example, the grinding wheel may be movably mounted so that as wear occurs, the wheel moves closer to the substrate. Such an arrangement may be suitable for a continuous grinding operation, but not if the grinding wheel contacts multiple spaced substrates. In that case a freely movable wheel would drop into the spaces between substrates damaging the wheel, as well as the edges of some substrates such as glass.